1. Field of the Invention
The present invention relates to intraocular lens. More particularly, the present invention related to intraocular lens having an outwardly extending elongate supporting body, or haptic, which is formed from an elongate cylindrical body. Still more particularly, the present invention relates to such a haptic, and to a method of making the haptic.
2. Related Technology
A conventional intraocular lens includes a principal refractive body, known as the lens optic, and one or more support structures for positioning and retaining the lens optic in a generally centered position within the anterior or posterior chamber of the eye. These support structures are generally elongate, filamentary-like structures, and are commonly referred to as "haptics". The haptics of an intraocular lens may be integral with the lens optic, or more commonly, are manufactured separately of the same or a different material than that which is used to make the lens optic. Commonly, the lens optic is molded about a head portion of the haptic which has securement features designed to mechanically engage with the material of the lens optic in order to provide a permanent and solid attachment of the haptic and optic one to another. Alternatively, a proximal end portion of the haptic may be adhesively secured, heat staked or otherwise fastened into an aperture of the optic body.
An important goal for intraocular lens designs is to minimize trauma to the eye when the lens is inserted through a surgical incision. Accordingly, an effort is made to ensure that the incision in the eye is kept to a small size. Also, biologically inert materials are used for the lens optic and the haptics. Additionally, the physical proportions of the lens and haptics are chosen so that the lens when resident in the eye does not interfere with, irritate, or damage the delicate tissues of the eye. On the other hand, the lens and haptics must be such that the lens optic is well supported and centered in the eye. Shifting about of the lens would be very distracting to the patient, and centration of the lens could be lost were the shifting to be of sufficient magnitude.
However, the characteristics for a material which makes it desirable for a lens optic frequently makes it undesirable for a lens haptic. The converse is also true of material selected for making of the haptics for the most part. Consequently, conventional intraocular lens are frequently made of two different materials. The lens optics are frequently made of polymethylmethacrylate (PMMA). This material is rather rigid, is easily cast or machined to shape, is biologically inert, and has excellent refractive and other optical properties for its function as a lens. Another material which is not rigid, and which is used to form flexible lenses which may be rolled or folded to ease their insertion into the eye via an incision which may be smaller than the size of the unconstrained lens, is silicone. This material has acceptable optical properties and does provide a lens with the possibility of reducing the incision size required for its insertion.
On the other hand, PMMA is rigid and in its ordinary material condition is too brittle and stiff for use in making a haptic. That is, the manipulations, and folding, for example, which a haptic must endure during the surgical insertion of the lens into the eye are too much for this relatively rigid and somewhat brittle material to endure. Moreover, elastomeric materials, such as silicone do not perform well as a haptic because they are too flimsy. Except in a broad flange configuration of lens design, which is not as desirable as the lens designs using cantilevered spiral filamentary haptics, silicone does not provide an acceptable support to the lens optic. In other words, haptics must be simultaneously pliant enough to avoid damage to delicate eye tissue and to allow deformations of the haptics during surgical implantation of the lens, and at the same time be rigid enough to act as a support structure.
The result has been an evolution toward multi-piece lenses with elongate cantilevered spiral filamentary haptics. The material of the haptics is generally polypropylene in a filamentary form. The filamentary polypropylene haptics are staked, bonded, embedded by molding the optic around a head portion of the haptic, or are otherwise secured to the lens optic. Some haptics are formed with various anchor or head features which assist their securement into the lens optic at a peripheral part thereof. U.S. Pat. Nos. 4,880,426; 4,8894,062; 4,790,846; 4,888,013; and 4,978,354; disclose lens and haptic designs which are conventional.
Nevertheless, and even in view of the numerous intraocular lens designs with their various optic and haptic designs which are conventional and known, there still exists a desire and a need for improved intraocular lens with improved haptics having better physical properties, improved handling qualities during surgical implantation, decreased costs of manufacture, eased quality control in manufacture, improved flexibility in the design of the haptic resulting from its method of manufacture, and other considerations which bear upon the overall utility of the lens and haptic combination as it is made available to the physician and patient.